Skeletal Muscle

• Alpha motor neuron innervates # of muscle fibers
• To excite a cell need to highly excite a negative cell TO POSITIVE
• Pottasium can go in and out without the NAK pump
• Cross Bridge Cycling Process (myosin pulling actin towards middle)

  • Step 1: Cross Bridge Formation (Binding)
  • Myosin globular heads attach to actin

  Step 2: Powerstroke (Bending)

  • Pulls the actin

  Step 3: Cross Bridge Detachment (Braking)

  • Myosin releases actin and requires ATP

  • Step 4: Reactivation of Myosin (Bouncing)
• 1. Neuron depolarize

  2. Ach moves to end of axon

  3. Ach binds to receptors on motor end plate

  4. This opens sodium gates, flows into cell and overwhelms cell to be positive

  5. Internal charge becomes positive in skeletal muscle

  6. This moves down to t-tubule and calcium cates are triggered and bind to troponin

  7. Triggered by charge change
• Joint Kinesthetic Receptors

  • Sensitive to angles

  Muscle Spindles

  • Sensitive to muscle length, muscle stretch (rate of change)

  Golgi Tendon Organs

  Sensitive to tension in tendon and strength of contraction
• *Intrafusal(inside and horizontal)/extrafusal nerve(outside) and where muscle spindle is (inside and vertical) -sends signal through gamma and alpha

  *Golgi tendon is where tendon/muscle meets to prevent PCL tear
• Alpha vs Gamma Motor Neuron:

  • Alpha motor neurons innervate extrafusal fibers, the highly contracting fibers that supply the muscle with its power. 

  Gamma motor neurons innervate intrafusal fibers, which contract only slightly.
• Inverse Myotatic Reflex vs Stretch Reflex

  • The stretch reflex is when a high force causes muscles to relax
  • The inverse myotatic reflex is when stretch causes a reflex contraction
• Resting Membrane Potential:

  1. Cell depolarizes due to sodium channels opening
  2. Membrane potential becomes positive
  3. Cell Repolarizes as potassium channels open and sodium channels close, and it leaves cell
  4. In hyperpolarization even more potassium leaves cell